The present invention relates in general to cylinder-type key locks having a plurality of key set tumblers, and more particularly to key-operated rotary plug cylinder locks utilizing a key plug whose rotation is controlled by a plurality of rotary disc-type tumblers operated by a key having an angled bitting formed from a generally round key and also having a plurality of pin tumblers positioned by the key set tumbler discs.
One of the common types of key locks which have come into wide use is the type known as a cylinder lock. Conventional cylinder locks normally comprise a relatively fixed housing forming the lock body or casing having a cylindrical bore opening through the front or rear face of the lock body which rotatably houses a rotating cylinder or plug assembly. The rotatable cylinder or plug assembly has a keyway or key slot opening through the front or rear face of the cylinder or plug and extending over most of the axial length thereof, as well as one or more resiliently urged tumblers formed of rotatable or slidable members which normally occupy positions crossing the shear zones or interface zones at boundaries between the rotatable cylinder core or plug and the outer body or shell preventing rotation of the core relative to the body or shell. When a key of proper contour or combination surfaces is inserted in the keyway or key opening in the cylinder core or plug, the contoured key surface aligns the resiliently urged tumblers in such a way that a parting line, either of the tumbler members or of some other locking member coactive with the tumbler members, is brought into coincidence with the interface plane at the shear zone, or the locking member is withdrawn from interference in the path of the interface plane or peripheral surface of the core or plug. Thus, when all of the tumblers are properly aligned by the contoured key surface, rotational forces applied to the key permit the core or plug to turn through the normal motion involved in moving the lock, from a locked to an unlocked condition.
Due to conditions which arise in the construction of the lock parts under normal manufacturing tolerances, it has been possible in cylinder locks which are not provided with special pick resistant features to achieve unauthorized operation of the lock by such picking techniques as inserting a picking tool into the keyway and exerting a torque on the plug so that with careful movement of the plug in selected directions, the resiliently urged tumbler first placed in compression by torquing the plug is aligned by the pick for clearance at which point the plug rotates a minute degree to bring the next resiliently urged tumbler into a similar compressed condition and is aligned by the pick for clearance, and this succession of operations is repeated until all of the tumblers have been aligned to permit the plug to be rotated.
One of the most common types of cylinder locks is the pin tumbler type cylinder lock, wherein segmented tumbler pins formed of lower key engaging pin segments and upper drive pin segments have a line of separation between the segments which is normally displaced from the interface plane or the shear line of the plug but is positioned by the proper key so that the line of separation of all of the pin tumblers align with the plug shear line and permit rotation of the plug. Such pin tumbler type cylinder locks have been particularly susceptible to the above described types of picking techniques, and many attempts have been made to provide them with resistance to such picking operations. In some cases, the pin tumblers have been so constructed that the tampering by picking techniques with one of the tumbler pins automatically locks the remaining tumblers against further movement, or additional recesses have been provided in the outer cylindrical casing so that after a pin tumbler has been picked it re-engages in the absence of clearance of the remaining pin tumblers, or lock out devices have been provided so that attempts to pick one or more of the pin tumblers results in additional locking pins being activated to lock the plug against rotation even by authorized persons.
To increase resistance to picking by the techniques which are successful with pin tumbler type cylinder locks, cylinder locks of the rotary disc tumbler type have come into wider use. A popular type of rotary disc tumbler cylinder lock is the so-called Abloy lock, wherein a bank of peripherally gated rotary locking discs housed within a rotatable sleeve member have shaped center apertures which respond to a proper key surface to align the gates to permit radially inward movement of a locking bar which normally traverses the shear line between the rotary sleeve and an outer fixed cylinder casing. Such rotary disc tumbler type cylinder locks may be of the general type disclosed in U.S. Pat. Nos. 3,771,340 or 3,621,689, or 3,848,442, with or without related features of other patents obtained by the Finnish corporation Oy Wartsila Ab relating to the Abloy lock. Unauthorized detection of such rotary disc tumbler cylinder locks has been achieved, however, by techniques such as introducing a picking probe or similar tool into the key opening to interpose an offset shaped extension thereof between the faces of successive rotary disc tumblers and manipulating the probe to detect the position of the key engaging shoulder formation and/or of the peripheral gates of the respective tumblers by observing the angular position of the probe externally of the lock and determine therefrom the key combination or shaped surface contour of the key for that lock. Also, techniques of torquing the cylinder or plug of such locks in a special manner to distort metal from some of the lock components into normally vacant spaces within the lock by application of strong torquing forces to the cylinder or plug have resulted in authorized penetration of the lock.
I have recognized that in some applications for cylinder type locks in areas where a higher degree of security is required than is available from the conventional pin tumbler type cylinder lock or the rotary disc tumbler type cylinder locks, higher security characteristics providing greater pick resistance and greater resistance to torque lock penetration techniques can be achieved by combining features of the disc tumbler type locks with features of pin tumbler type locks to introduce features of both types of locks into one cylinder lock construction.
Accordingly, an object of the present invention is the provision of a novel rotary plug cylinder lock having rotary disc type tumblers and pin tumblers, constructed to resist unauthorized detection of the key combination for the lock and resist unauthorized penetration of the lock by torquing or picking techniques.
Another object of the present invention is the provision of a rotary plug cylinder lock as described in the immediately preceding paragraph, wherein the key plug is freely rotatable through a full 360.degree. unless all of the pin tumblers are properly positioned so that their line of separation is registered with the plug shear line.
Another object of the present invention is the provision of a novel rotary plug cylinder lock as described in the two immediately preceding paragraphs, wherein the key never comes into contact with the tumbler pins, thereby improving security of the lock.
Yet another object of the present invention is the provision of a novel rotary plug cylinder lock as described in the three immediately preceding paragraphs, wherein the lock is readily adaptable to right hand or left hand operation by cutting the key in either clockwise or counterclockwise directions and assembling the disc tumblers and pins to the correct spacing and depths.
Other objects, advantages, and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating a preferred embodiment of the invention.